1. Field of the Invention
The present invention relates to a circular braiding machine for braiding strands and, more particularly, to a circular braiding machine with a rotation axis, the circular braiding machine comprising a group of inner spools and another group of outer spools, each spool carrying a single strand, and each group arranged on a respective circular track coaxial to the rotation axis and movable in opposite directions and means for crossing the strands of the inner and outer spools. It also relates to a device for strand guiding in this circular braiding machine comprising a strand guide part or guide device arranged between a first spool and a braiding point for a strand fed to the braiding point from the first spool, which is movable back and forth for crossing the first strand over at least one second strand coming from a second spool so that the length of a section of the first strand between the first spool and the crossing point continuously changes, and a device for compensating these length changes having at least one movable guide element for the first strand arranged between the first spool and the guide part or guide device.
2. Prior Art
In the known circular braiding machine of this type, for example as described in German Patent Documents DE 44 22 893 A1 and DE 195 47 930 A1, the strands of material being braided coming from the outer and inner spools are guided with guide devices to the braiding point, which are movable back and forth inclined to the rotation axis in order to cause crossing of the concerned strand according to the rapid braiding principle with the strands coming from the outer and inner spools. The motion of the guide devices occurs, among other reasons, with the help of crank elements and push rods so that the guide devices or parts execute an essentially sinusoidal motion about the rotation axis of the circular braiding machine, however they accelerate in the region of the crossing point and are delayed at the turning point regions in order to avoid whip-like back and forth motions.
The motion of the guide devices or parts has the result that the length of the strand sections located between the outer spools and the braiding point continuously changes during operation. Thus a compensation device must be provided for each outer spool, which temporarily stores an excess strand portion and delivers this strand portion on demand in order to avoid sagging or tearing of the strands. A compensation device of this type usually comprises pivoting plates acted on by spring forces and rollers attached to them that must be in a position to compensate for length changes of up to about 50 mm. This has the disadvantage that somewhat expensive springs are necessary which have a constant characteristic curve over the entire compensation range. This is not always attainable and a variation of the tension within the above-described strand section occurs as a result. Furthermore this type of compensation device has a certain inertia because of the masses being moved, which can lead to tearing of the strands or the threads or filaments forming them at high rotation speed.